Showing papers on "Supercapacitor published in 1991"
TL;DR: The transition between battery and supercapacitor behavior arising from a range of degrees of oxidation/reduction that arise over an appreciable range of potentials is discussed in this article.
Abstract: The storage of electrochemical energy in battery, "supercapacitor," and double‐layer capacitor devices is considered. A comparison of the mechanisms and performance of such systems enables their essential features to be recognized and distinguished, and the conditions for transition between supercapacitor and "battery" behavior to be characterized. Supercapacitor systems based on two‐dimensional underpotential deposition reactions are highly reversible and their behavior arises from the pseudocapacitance associated with potential‐dependence of two‐dimensional coverage of electroactive adatoms on an electrode substrate surface. Such capacitance can be 10–100 times the double‐layer capacitance of the same electrode area. An essential fundamental difference from battery behavior arises because, in such systems, the chemical and associated electrode potentials are a continuous function of degree of charge, unlike the thermodynamic behavior of single‐phase battery reactants. Quasi‐two‐dimensional systems, such as hyperextended hydrous , also exhibit large pseudocapacitance which, in this case, is associated with a sequence of redox processes that are highly reversible. Such oxide redox systems give rise to the best supercapacitor behavior and capacitances of farads per gram can be achieved. Other examples are the conducting polymer electrodes and Li intercalate systems. These systems provide examples of the transition between battery and supercapacitor behavior arising from a range of degrees of oxidation/ reduction that arise over an appreciable range of potentials. The impedance behavior of an supercapacitor is illustrated but is far from that expected for an electrostatic capacitor.
2,000 citations
TL;DR: In this article, Arc cast Cu-Ta and powder processed Al-Ta composite alloys have been examined as potential materials for making electrolytic capacitors, and three alloys were deformation-processed into sheet and rod form and then processed through anodization, electrolyte formation and cathode fabrication steps to make prototype capacitors.
Abstract: Arc cast Cu-Ta and powder processed Al-Ta and Al-Nb composite alloys have been examined as potential materials for making electrolytic capacitors These two phase alloys can be severely cold-worked, deformation-processed, to produce Ta surface areas considerably larger than those possible with the powder processing used in current Ta capacitors The three alloys were deformation-processed into sheet and rod form and then processed through anodization, electrolyte formation and cathode fabrication steps to make prototype capacitors The capacitors were tested for capacitance, effective series resistance and leakage The figure of merit,CVg−1, (capacitance × voltage per gram) values obtained closely approached those of currently manufactured capacitors but dc leakage values were unacceptably high using a solid electrolyte To realize the full potential of this new method for fabricating Al-Ta capacitors further research is required to improve the deformation of the Ta powders and to find methods of anodization and solid-state electrolyte formation capable of maintaining oxide film integrity
1 citations
Patent•
05 Aug 1991
TL;DR: In this paper, a pyrrole based conductive polymer and a composition containing a specified ionic group are used to obtain an electrochemical energy storing unit having a high energy density and a long cycle time.
Abstract: PURPOSE: To obtain an electrochemical energy storing unit having a high energy density and a long cycle time by employing a pyrrole based conductive polymer and a composition containing a specified ionic group. CONSTITUTION: The electrochemical energy storing unit employs a conductive polymer selected from polypyrrole and/or substituted polypyrrole, and a composition containing an ionic group including at least one R-sulfate group or R sulfonate group (R is alkyl group or aryl group). Normally, it contains 0.01-0.9 parts of ionic group per 1 part of pyrrole and/or substituted pyrrole and it is doped with cations or anions. Doping is performed preferably in a solution of propylene carbonate, e.g. LiClO4 . The composition can be employed in the electrode of a capacitor, a battery, a cell, etc., and an anode comprises a film of the composition or an electrode coated therewith. A super capacitor employing the composition has an electrode capacity of at least 120 F/1g of electrode and a rechargeable generator has an element exhibiting mass capacity of at least 4mA.h stored during discharge.
1 citations
Patent•
24 Oct 1991TL;DR: In this article, the engine starter motor is mounted on a bank of capacitors, which can store sufficient energy to operate the motor for starting the engine, and small wires are used to connect the motor to the battery, which may be of lower weight and volume than normal and may be remote from the engine compartment.
Abstract: The engine starter motor 4 has mounted therein or thereon a bank of capacitors 5 which can store sufficient energy to operate the motor 4 for starting the engine. Smaller wires can thus be used to connect the motor 4 to the battery 1, which may also be of lower weight and volume than normal and may be remote from the engine compartment. The capacitors 5 may be molecular or double layer supercapacitors, eg. thirteen 0.9 volt 7800 Farad capacitors, and the battery 1 may be a 20 Ah gas-recombination type.
1 citations